import java.util.Arrays;
import java.util.List;

class Demo3_1_4_5_1 {
    public static void main(String[] args) {
        List<List<Integer>> list = Arrays.asList(
                Arrays.asList(1, 2, 3)
                , Arrays.asList(4, 5, 6)
                , Arrays.asList(7, 8, 9, 10, 11, 12, 13)
        );

        System.out.println("--------------- combineList 前");
        System.out.println(list);
        System.out.println("--------------- combineList 后");
        List<Integer> combinedList = list.stream().collect(CustomCollectors.combineList());
        System.out.println(combinedList);
    }
}